The connectors with the o ring seals look as if they are "KF" or Kwik fittings. I have used those exclusively on my systems up to this time. They are fine for most vacuum systems up to and including 10e-6 torr. I would recommend Conflats for continuous service above 10e-5 though.
The blank off plate on the turbo is common where the turbo would be too efficient at full throttle/full throat. This is the case with a fusor as well. You really are running a fusor at about the level a simple forepump can achieve, but it is nice to really remove the air to a level three orders of magnitude below running pressure. This warrants only a few parts per thousand of gas other than D2 are in the chamber at 10 microns.
The problem is that the leak rate for D2 to maintain 10 microns of D2 pressure against a diffusion or turbo pump is very wasteful of deuterium gas. Thus, a forced throttle plate or variable vacuum valve assists in reducing the continuous flow volume of D2 gas. It is an effort to limit the pumping speed of a voracious pump working in molecular flow. Remember, in this regime the molecules are not sucked or, more properly, dragged through the hole, but wander through it randomly via richochets. the fact that you have 1000 turbine blades moving at super sonic velocities below the small hole is of little consequence to gas molecules on the other side.
Richard Hull
Created on Wednesday, March 14, 2001 10:49 AM EDT by Richard Hull